Molding machine



Sept. 26, 1944.

V. E. HOFMANN ET AL MOLDING MACHINE Filed April 29, 1941 5 Sheets-Sheet l ATTOR YS WY f 5 SheetsSheet 2 V. E. HOFMANN ET AL MOLDING MACHINE Filed April 29, 1941 III/l n iw gg Sept. 26, 1944.

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MOLDING MACHINE Filed April 29, 1941 5 Sheets-Sheet 3 INVENTORS 1 E Hofmann v BY JM Blank ATTOR YS Sept. 26, 1944.

v. E. HOFMANN ET AL MOLDING MACHINE 5' Sheet Sheet 4 Filed April 29. 1941 INVENTORS V. I7. .Hofma. nn

ATTOR EYS P 1944- v. E. HOFMANN ET AL MOLDING MACHINE Filed April 29, 1941 5 Sheets-Sheet 5 INVENTORQS may)" JMBZan/r,

ATTORNEYS VT Effof Patented Sept. 26, 1944 2,359,216 MOLDING MACHINE Victor E. Hofmann. and John M. Blank, Toledo, Ohio, assignora to Owens-Illinois Glass Company, a corporation of Ohio Application April 29, 1941, Serial No. 390,934

17 Claims.

Our invention relates to mechaniism for maks hollow articles of thermoplastic material such as organic thennoplastics which are softened when heated so that they can be molded or blown to desired shapes and then cooled and hardened.

ing stations for the several operations, said machine being adaptable with minor adjustments In th patent to Victor E. Hofmann, No.

2,348,738, May 16, 1944, Making hollow thermoplastic ware, there is disclosed a method by which blanks or p'reforms of such thermoplastic materials may be heated to render them soft and plastic, then blown to finished form in a mold and quickly cooled and set within the mold by the application of a cooling fluid to the interior of the article while supported in the mold.

An object of the present invention is to provide a machine which is largely automatic in its operation, designed for producing articles by such method rapidly and efficiently.

Thermoplastic materials adapted for making hollow articles vary widely in their characteristics and working requirements such as the temperatures at which they must be worked, softening temperatures, setting temperatures, heat conductivity and rate of heating and cooling, and length of time required for molding and curing in the molds. Working conditions and requirements also differ greatly for different articles, depending uponsize and shape 01 the articles, the' thickness of the walls of the articles, as well as the materials of which they consist. An object of the present invention is to provide a machine which is readily adjustable to meet these various requirements, thereby adapting it to the manufacture of a wide variety of thermoplastic articles and for use with various molding materials.

A further object of the invention is to provide a machine comprising an intermittently rotating carriage on which the hollow blanks are placed and each brought to a number of operating stations in succession at which the several operations of the methodare effected, including a heating station at which the blanks are enclosed in a heating chamber and heated to render them plastic, a blowing station at which the softened blanks are blown within a mold to finished form, a cooling station at which the articles are cooled in a cooling mold, and mechanism by which the various operations are carried out and synchronized.

A further object of the invention is toprovide a machine including a plurality of heating stations and a plurality of molding stations together with an intermittently rotating carriage by which the. blanks of thermoplastic material may be,

brought in succession to the heating and moldfor fabricating the articles in groups]; plurality of blanks being simultaneously heated at the several heating stations and then transferred in a group to the several molding stations, and the molding and cooling operations for the several blanks being effected concurrently at said molding stations. o

Other objects or the invention will appear hereinafter.

Referring to the accompanying drawings:

Fig. 1 is a sectional elevation of a machine constructed in accordance with the present invention;

Fig. 2 is a fragmentary sectional elevation of the upper portion of the machinathe section being taken through a blow mold.

Fig. 3 is a plan view of the machine, one of the molds being shown in section.

Fig. 4 is a sectional plan view showing particularly the driving mechanism for the work carriage and cam shafts.

Fig. 5 is a part-sectional elevation showing a piston motor for lifting the heating drums.

Fig. 6 is a diagrammatic plan view of a modified form of driving mechanism.

Fig. 7 is a fragmentary elevation. showing valves and their operating cams controlling the blowing and cooling operations.

Fig. 8 is a plan view of the same.

Fig. 9 is a sectional plan showing particularly the rotary work table.

Referring to the drawings, the machine comprises a framework III on which is mounted a lower platform ll supporting the driving mechanism and an upper platform II. An intermittently rotated carriage includes a circular work table ii on which an ,annular series of workpiece supporting plates 14 is mounted. The work table is bolted toa hub II (Fig. 2) keyed to a vertical shaft It for rotation therewith. The shaft is iournalled in a bearing head I! bolted to a standard It mounted on the platform II.

The driving mechanism for rotating the carriage includes an electric'motor 20 which may i be driven continuously. The motor as shown is mounted on parallel rods 2| and is adjustable therealong by a hand crank 22 on an adjusting shaft 23. The motor has driving connection 7 through a belt 24 and pulley 25 with a worm shaft 26 which drives a worm wheel 21 keyed on a shaft 28. A pinion 28 on the shaft 28 drives a gear 30 one. vertical cam shaft 3 l.

The carriage is driven intermittently, step by step, by means of a Geneva drive including a Geneva gear wheel 32 keyed to the carriage shaft l3. An arm 33 having a fixed mounting on the shaft 28 carries a rock arm 33 connected thereto by a pivot 33. The rock arm operates to move a pin 36 up and down in the arm 33. The rock arm 33 is swung upward to the position shown in Fig. 1 by a tappet 31 keyed to the shaft 3| and arranged to engage a roll 38. The arm 33 is held in its lifted position by a coil spring 38. A cam 33 on the shaft 3| is adapted to strike the arm 33 and start it downward, the spring 33 then completing its'downward movement into position to drive the Geneva gear 32. The diameters of the gears 28 and 33 are in the ratio of 1 to 2 so that the shaft 28 makes two rotations for each rotation of the shaft 3|. During one rotation of the shaft 28, the driving pin 38 is in its lowered position and engages one of the radial slots 3| in the gear 32 and imparts a step rotation thereto. The tappet 31 then lifts the pin 38 to an inoperative position so that the carriage remains at rest during the next rotation of the shaft 28. The carriage is held stationary by a brake 32' (Fig. 4)

Each of the plates i3 (Fig. 2) hasmounted thereon a tubular work-holder 32. Extending through said holder is a tubular shaft 33 carrying a head 33, said shaft having a limited up and down movement within the holder 32, permitting said head to clamp a hollow blank or preform 33 onto the holder. A tubular rod 33 extends lengthwise through the tube 33 and has a limited up and down movement relativeto said tube. A coil spring 31 holds the rod 33 in its lowered position in which a head 33 on the upper end of the rod is in sealing engagement with the head 33.. The tube 33 is held in its lowered position for piston motor 33 (Figs. 1 and 2) comprising a cylinder 33 supported on the frame 33 by means of a strap 38. the cylinder being free for sliding movement lengthwise in said strap. The motor includes a piston 33 and piston rod 31, the latter connected directly to the mold section 3|. The motor cylinder is connected to the mold section 33 by apair of bars 83. when air under pressure and its motor, is bolted taohed to one end of a cross-beam or frame 13 by a pivot is admitted to the inner end of the motor cylinder (Fig. 2), the piston moves to the right, withdrawing the mold section 8| to the dotted line position where it is arrested by a stop 33. The pressure within the cylinder then reacts to move the cylinder to the left, thereby moving the mold section 32 to the dotted line position. thus oompleting the opening of the mold.

The frame 32, which carries the blow mold 33 or otherwise rigidly atextending transversely of the machine and mounted to rock about a pivot 1| supported on a standard 12 rising from the platform l2. A.

frame 32 similar to the frame 32 is attached to the opposite end of the beam 13 and carries at station c a mold 13 and its operating motor 13' which may be in all respects similar to the mold 33 and motor 33. The mold 13 serves in certain methods of operation, as a eoolmg mold in the manner hereinafter described.

-- The beam I3 is rocked for lifting and lowering the molds, by a piston motor 13 pivotally mounted at 18 on the platform l2 and comprising a motor piston rod 18, the outer end of which is connected 11 to a pair of angle bars 13 fixed to the beam 18. The operation of the piston motor 13 is controlled by a valve 18 (Figs. 1 and 4) which gripping the blank by means of a pair of cams 38 adapted to rock on pivot pins 33 on a collar 3| on the tube 33. Screw threaded lock nuts 3| are provided on the tube 33 for vertical adiustment of the collar 3|. The cams may be rocked by a handle 32 (Fig. 1) to release the tube 33 and permit it to be lifted by springs 33 for releasing the work-piece.

The machine is designed and adapted for various modes of operation, and as the description of the mechanism proceeds, one method of operation will be set forth, followed by a description of other methods. In accordance with one such method, the ope'i ator places blanks 33 on the work-holder 32 at a loading station a (Fig. 3), and as the carriage is rotated step by step, each work-piece is brought in succession to stations 0., b, c, d, e and I. At stations b and c, the blanks are enclosed in heating cups or drums 33 which may be heated by electric coils or other heating means, thereby providing heating chambers in v finished form in a blow mold at station d. The

heating drums 33 are carried on a pair of arms 33 attached to the upper end of a vertical bar 33(Flgs. 1, 3 and 5). The lower end of the bar 33 is attached to a piston rod 31 of an air operated piston motor 38 by which the heating drums are periodically lifted and lowered under the control of valve mechanism as hereinafter described.

The blow mold 58 at station 1 comprises partible sections 30 and 3| mounted for reciprocating movement on a carrier frame 82. The mold is opened and closed by means of an air operated opens a pressure line 83 alternately to pipes '33 and 83 'leading to the upper and lower endsrespectively of the motor cylinder. The valve is operated by a cam "secured to the shaft 3|. As the shaft rotates the cam operates to swing an arm 8| about a pivot 32. g This moves the valve stem inwardly, thereby opening the pressure line 33 to the pipe 83. This operates to lower the motor piston and swing the beam 13 about its pivot 1|, thereby lifting the molds which at this time are in open position. When the cam 33 runs 0! the arm 8|,the valve 13 is reversed, thereby connecting the pipe 83 to the pressure line so that the motor 13 operates to lower the molds. The valve 18 is of conventional construction for connecting each of the pipes 33, 33 the other is connected to the pressure line. The air motor 38 is also controlled by the valve 13. Pipes 83' and 83", corresponding to the pipes 33 and 83, extend from the motor 38 to the valve, so

that the air motors 38 and 13 operate simultaneously for lifting the heaters 33 and the molds. and also lower them simultaneously.

After the blow mold 33 has been lowered and closed around a blank 33, the latter is blown to its finished form within the mold. The air pres sure system for supplying blowing air to the blanks comprises a pipe 83 and a swiveled coupling 88 (Fig. 1) through which air under pressure is conducted from any suitable source (not shown) into a channel 81 (Fig. 2) extending downwardly through the upper end of the shaft I8. A plug 88 separates the channel 81 from a passageway 83 extending downward to the lower end of the shaft. Distributing heads 83 on opposite sides of the shaft l8 are tapped into the to exhaust when the work-piece holders. The pipes 9I extend downward through openings in the table I3 and are connected to valves 92 mounted in frames 93 attached to the lower ends of posts 93 depending from the table. Each pressure line is continued from its valve 92 through a pipe connection 92 I to a Junction box 92 and thence through a flexible hose 94 to an elbow 95 attached to the lower end of the tubular rod 49. Check valves 92 are provided to prevent reverse flow of the fluids in the various lines.

Cam mechanism for actuating the valves 92, for lifting the rods 49, and for controlling the application of cooling fluid to the molds, includes two cam shafts 99 and 91 (Figs. 1, 3 and 7) mounted in bearings on the machine frame. Each cam shaft carries a bevel gear 99 running in mesh with a gear 99 keyed to the upper end of the shaft 3|. Keyed to each of the shafts 96 and 91 are cams IOI, I02 and I03. The cam IOI operates through a cam roll I04 and lever I05 fulcrumed at I09, -to move the valve stem I 01 inward and thereby open the valve 92. This establishes the air pressure linethrough said valve to and through the rod 49 into the mold for blowing the blank to final form. After the blowing operation is completed, and the valve 92 again closed, the cam I02 operates to lift the rod 49 and head 49,

thereby opening a passageway from the interior of the blown article downwardly between the rod 49 and tube 43 to an outlet I09. The cam I02 operates through a roll I09 carried on an arm II pivoted at III, said arm carrying an adjustable contact piece II2 to engage the elbow 95.

If desired, the blown article may be cooled while still enclosed in the blow mold 59 by means of water, air or other cooling fluid. The cooling fluid is introduced at the lower end of the shaft I9 through a swiveled pipe connection 89' and extends upwardly through the passageway 89 and is distributed by heads to pipes IIB. individual to the work-holders. The pipes II6 extend to valves III mounted beside the valve 92 in the frames 93. The valves II! are under the control of the cam I03 on theshaft 99 while at the blowing station (1, provided the cam is in operative position on the shaft, and are actuated by said cam operating through a cam roll H3 and an arm H4 in the same manner as above described in connection with the valves 92. The cam I03 is timed to open its valve III while the stem 49 is held in its lifted position by the cam I02. The valve III has a pipe connection H8 with the junction box 92 and thence through the pipe 94 with the rod 49 so that when the valve II! is opened, the cooling fluid is admitted to the blown article and may be applied in the form of a spray to the interior surface of the article. The cooling fluid is discharged through the outlet pipe I09, trough H9 and pipe I (Fig. 1). After the valve II! has been closed and while the rod 49 is still in an elevated positiom-the valve 92 may again be opened for an instant in order to blow out any remaining quantity of coolant.

The operation of the piston motor 63 for opening and closing the blow mold 59 is controlled by of electric current supply. A switch I30 is also connected in the electromagnet circuit and is closed by an adjustable contact piece "I on the frame 92 when the mold is swung downward to operative position, the switch I30 being automatically opened when the mold is again lifted. While the mold 59 is in its lifted position it is also held open.

When the mold is swung downward for enclosing the blank, the closing of the switch I30 oompletes a circuit for the electromagnet winding, the contacts I29 being in closed position at this time. This causes the electromagnet to actuate the valve I22 and thereby open an air pres sure line through the valve and a pipe I32 (Fig. l) to the outer end of the motor cylinder so that the piston is moved inwardly to close the mold. The mold remains closed until the high portion of the cam I25 runs off the cam roll and per mits the arm I29 to be lowered by a spring I33 so that the rod I29 operates to separate'the contacts I29, thereby deenergizing the electromagnet and reversing the valve I22. This establishes a pressure line through the valve and a pipe I34 to the inner end of the motor cylinder so that the motor operates to open the mold. The mold is then swung upward in the manner heretofore described. As the magnet circuit is always open at the switch I except when the mold is in its lowered position, closing of the mold while the mold is lifted is positively prevented.

The blow mold as may be heated by electrical heating elements I35 (Fig. 3) automatically controlled in a conventional manner'for main the mold'at any temperature son before it has been completely expanded to the ture is lowered sufficiently to solidify or set the thermoplastic material so that it will retain as (III shape. This cooling" operation may cool the m lds to some extent but such cooling does not penetrate the mold walls to any great depth, so that the mold is quickly reheated to operating temperature by the heating elements 235.

45 above described, the cooling and setting ,of the blown article may take place within the mold 59, the application of cooling fluid being under the control of the cam I03. If desired, however, the cooling operation may be deferred until the article has been transferred to the mold 13 at station 6. To accomplish this, the cam I03 is shifted lengthwise of the cam shaft to an in0perative posit on as shown in Fig. '7 so that the valve III at station D remains closed. The cams MI and I03 on both the cam shafts 99 and 91 are preferably shiftable individually into and out of upon'the particular method in use and desired order of the blowing and cooling operations.

a valve I22 (Fig. 2) actuated by an electromagnet I23, the valve and electromagnet being mounted within a control box I24 (Fig. l). The electromagnet in turn is controlled by a cam I25 on the cam shaft 96 (Figs. 2 and '7). Said cam operates a lever I26 fulcrumed at I2! and carrying a rod I 29 which, when depressed, separates a pair of switch contacts I29 in the circuit of the electromagnet which is connected to any suitable source A-suming that the cam I03 at the station d is in its inoperative position (Fig. 7) so that no cooling operation takes place at this station, the blown article will remain in a more or less heated and plastic condition during itstransfer to the station e and its enclosure within the mold I3.

-It may then be necessary or desirable to apply a secondary or final application of blowing air to the article if it has shrunk or become distorted or out of shape during the transfer, this final blowing serving to restore it to perfect form and maintain it in such form until it has been cooled. The final blowing at station 6 is under the conwhich may be required for preventingundue chilling of the part-1' 4- I assume trol of the cam IIlI at said station. If desired, the mold I3 may be provided with electrical heating elements such as above described in connection with the mold 59.

After the final blowing in the mold I3, the cam I02 at this station may operate as before dethe cam I02 being set for this purpose, and circu lating air through the article under the control of the vcam IOI.

A further method which may. be employed consists of blowing the parison first in the blow mold at station d and without thereafter applying a cooling liquid at said station, transferring the article to station e, and blowing it in the mold 13, the latter being kept cool or comparatively cold so as to chill and set the article without requiring the application of a coolirm liquid.

In accordance with the above described methods of operation the mold carriage is given step rotations through angles of 60 each, bringing each mold to rest at each of the six stations in succession. In the manufacture of some articles it is practical to complete the heating of each blank or preform in a single heating cylinder 54 and to effect the blowing and cooling operations in a single mold. This with the machine disclosed permits two articles to be completely heated at the same time in the two heating chambers, and two other articles to be blown and cooled concurrently in the two molds, so that the output of the machine is thus doubled or multiplied. This requires the mold carriage to be indexed through 120 instead of 60 at each step rotation.

Fig. 6 illustrates a modified form of driving mechanism for this purpose. As here shown, the Geneva wheel 32 may be formed with only three radial slots 4i. Intermeshing gears I36 and I3! of equal diameter are mounted on the shafts BI and 28 respectively, these gears replacing the gears 30 and 29 (Fig. 1). The arm 33 in this instance carries a pin I38 fixed to the arm for engaging the slotted wheel 32. The latter is thus indexed once during each rotation of the shaft 28 and through an angle of 120. With this construction the tappet 31 (Fig. 1), cam 40 and lifting arm 34 are unnecessary and may be omitted.

In operating the machine with this modified form of drive the operator places blanks on the holders 42 at stations a and I after each step rotation of the carriage. These blanks are thus brought to the two heating chambers at stations 22 and c simultaneously and are heated to the required temperature at said stations. The next step rotation of the carriage brings the two heated blanks to stations d and e where they are enclosed in the two molds 59 and 13. The operations at these two stations are preferably identical. These may comprise blowing the articles in the molds under the control of the cams IOI. The cams I02 may then operate to lift the rods 36 and vent the molds. This operation may be succeeded by the application of a cooling fluid under the control of the cams I03. Air may then be circulated for drying the article under the control of the cams Ill. The next step rotation of the carriage brings the completed articles to stations a and f and they are then removed from the machine.

Electricv current may be supplied to heating elements I" in the plates I, from any suitable source of current, through a distributor I (Figs. 1 and 2) comprising collector rings IlI engaging stationary contacts I42. Three collector rings are shown, permitting current to be drawn from either a three-phase or two-phase alternating current system or a direct current system. The current is supplied to the heating elements either at predetermined periods during the cycle of operations or continuously as desired. For example, the plates Il may be electrically heated while the blanks are being heat treated in the molds and/or heating cylinders,

to maintain the holders 2 at the desired temperatures.

Modifications may be resorted to within the spirit and scope of our invention.

We claim:

1. A machine for fabricating articles from thermoplastic materials, comprising a carriage, blank holders thereon, means for rotating the carriage intermittently step by step and thereby bringing the holders in succession to a blowing station, a blow mold at said station, a stationary support on which the mold is mounted independently of the carriage, means for closing the mold around a blank at said station, a tube project.- ing into the blank while the latter is enclosed by the mold, means cooperating with said tube for sealing the open end of the blank, means including an air pressure line extending to said tube for supplying air under pressure through said tube and thereby blowing the blank within the mold, a valve in saidline controlling said air supply, means for venting the blank to the atmosphere, means for conducting a cooling liquid through said tube and spraying the interior surface of the blown article therewith, a valve controlling the flow of said liquid to the said tube, automatic means for actuating said valves in succession in a predetermined time relation, and means for blowing drying air through said tube after said spraying and while the article is vented to the atmosphere.

2. A machine for fabricating hollow articles of thermoplastic material, comprising a carriage, an annular series of units thereon, each unit comprising a vertical tubular work-holder, a tube extending therethrough, a head on the upper end of said tube and of greater diameter than the interior of the work-holder, means for moving said tube up and down and causing said head to clamp the open end of a hollow blank to the upper end of the work-holder, means for rotating the carriage step by step and thereby bringing said units in succession to a blowing station, a partible blow mold at said station, a stationary support on which the blow mold is mounted independently of the carriage, means for closing the mold about a blank with the lower end of the mold closed about the upper end of the work-holder and with the mold extending upwardly from said work-holder, and means for supplying air through said tube for expanding the blank within the mold.

3. A machine for fabricating hollow articles of thermoplastic material, comprising a carriage, an annular series of units thereon, each unit comprising a vertical tubular work-holder, a tube extending therethrough, a head on the upper end of said tube and of greater diameter than the interior of the work-holder, means for moving said tube u-p'and down and causing said head to clamp the open end of a hollow blank to the upper end of the work-holder, means for rotating the carriage step by step and thereby bringing said units in succession to a blowing station, a partible blow mold at said station, a

stationary support on which the blow mold is mounted independently of the carriage, means for closing the mold about a blank with the lower end of he mold closed about the upper end extending therethrough, a head on said tube,

means for moving said tube up and down and causing said head to clamp the open end of a hollow blank to the work-holder, means for rotating the carriage step by step and thereby bringing said units in succession to a blowing station, a partible blow mold at said station comprising mold sections movable horizontally to and from a mold closing position, a piston motor, a support on which the motor and said mold sections are mounted, said motor comprising a piston connected to one mold section and a cylinder mounted for lengthwise reciprocation on said support, and means connecting the cylinder to the other mold section.

5. A machine for fabricating articles of thermoplastic material comprising a carriage, means for rotating the carriage step by step, blank holders on the carriage brought in succession to a blowing station by the rotation of the carriage, a sectional blow mold at said station, a supporting frame on which the mold sections are mounted for sliding movement to and from a mold closing position, a piston motor comprising a piston connected to one mold section and a cylinder slidable on said supporting frame and connected to the other mold section, said frame mounted to swing about a stationary axis for lifting and lowering the mold, and a mold lifting motor connected to said frame.

6. A machine for fabricating articles of thermoplastic material comprising a carriage, means for rotating the carriage step by step, blank holders on the carriage brought in succession to a blowing station by the rotation of the carriage, a sectional blow mold at said station, a supporting frame on which the mold sections are mounted for sliding movement to and from a mold closing position, a piston motor comprising a piston connected to one mold section and a cylinder slidable on said supporting frame and connected to the other mold section, said frame mounted to swing about a stationary axis for lifting and lowering the mold, a piston motor operatively connected to said swinging frame ers on the carriage and brought in succession by the rotation of the carriage to a plurality of molding stations, partible molds at said stations, supporting frames individual to said molds and each extending radially of the carriage, piston motors individual to said molds mounted on said supporting frames, said frames mounted to rock as a unit about a stationary horizontal axis and thereby swing the molds and their supporting frames up and down, and a motor connected for rocking said frames.

8. A machine for fabricating hollow articles of thermoplastic material comprising a carriage mounted for horizontal rotation, means for rotating the carriage, an annular series of workholders on the carriage, means cooperating with said work-holders for attaching hollow blanks thereto, said work-holders being brought in succession to a blowing station by the rotation of the carriage, a blowing mold at said station, means for closing th mold around a blank, a blowing system comprising air pressure lines individual to and communicating with said holders, valves in said lines, a cooling system comprising pipe lines individual to said holders through which cooling liquid is transmitted through the holders to the blanks while the latter are enclosed in the mold, valves in the cooling system and individual to said pipe lines, a cam shaft, cams thereon controlling respectively the valves in the air pressure lines and the valves in said cooling system, valve operating devices individual to said valves and brought into operative relation to said cams by said rotation of the carriage, and means for driving the cam shaft.

9. A machine for fabricating hollow articles of thermoplastic material, said machine comprising a carriage rotatable horizontally, work-holders on the carriage, means for rotating the carriage intermittently step by step and thereby bringing each work-holder to a plurality of heating stations in succession, heating drums indi vidual to said stations, a motor, operating connections between th motor and said drums for simultaneously lifting the drums as a unit, and

controlling means by which the drums are caused to be lowered for enclosing and heating blanks of the material at said stations and thereafter lifted and by which a lowering and lifting, of the drums takes place after each step movement of the carriage and while the carriage is stationary.

10. A machine for fabricating hollow articles of thermoplastic material, said machine com.- prising a carriage rotatable horizontally, workholders on the carriage, means for rotating the carriage intermittently step by step and thereby bringing each work-holder to a plurality of heating stations in succession, heating drums individual to said stations, a motor, operating connections between the motor and said drums for simultaneously liftin the drums as a unit, a blow mold, a motor for lifting and lowering the blow mold, valve mechanism controlling the operation of said motors, and means for actuating the valve mechanism in timed relation to the step movements of the carriage and causing the mold and heating drums to be lowered and lifted during each rest period between indexing movements of the carriage.

11. A machine for fabricating hollow articles of thermoplastic material, said machine comprising a carriage rotatable horizontally, work-holders on the carriage, means for rotating the carriage intermittently step by step and thereby bringing each work-holder to a plurality of heatin stations in succession, heating drums individual to said stations, a motor, operating connections between the motor and said drums for simultaneously lifting the drums as a unit, a blow mold, a motor for lifting and lowering the blow mold, valve mechanism controlling the operation of said motors, and means for actuating the valve mechanism in timed relation to the step movements of the carriage and causing the mold and heating drums to be lowered and lifted during each rest period between indexing movements of the carriage, said mold comprising partible sections, a motor operatively connected to said sections for closing and opening the mold, and electro-responsive means controlling said opening and closing of the mold and operable to prevent closing of the mold except when the latter is in its lowered position.

12. Thecombination of a carriage, means for rotating it step by step about a vertical axis, a work-holder on the carriage, a sectional mold, a supporting frame on which the mold sections are mounted, a motor operatively connected to the mold sections for closing and opening the mold, means for lifting and lowering the mold from and toward the carriage, and electro-responsive control means for preventing closing oi! the mold while in its lifted position.

13. The combination of a carriage, means for rotating it step by step about a vertical axis, a

work-holder on the carriage, a sectional mold, a supporting frame on which the mold sections are mounted, an air motor operatively connected to the mold sections for opening and closing the mold, an air pressure line to the motor, a valve in said line controlling the air supply to said motor, and electro-responsive means for automatically controlling the operation of said valve and preventing closing of the mold while in its lifted position,

14. The combination of a carriage, means for rotating it step by step about a vertical axis, a work-holder on the carriage, a sectional mold, a supporting frame on which the mold sections are mounted, an air motor operatively connected to the mold sections for opening and closing the mold, an air pressure line to the motor, a valve in said line controlling the air supply to said motor, an electromagnet operatively connected 'to said valve, means providing an electric circuit for the electromagnet, aswitch in said circuit, and means for actuating said switch when the mold is lowered to operative position.

15. The combination of a carriage, means for rotating it step by step about a vertical axis, a work-holder on the carriage, a sectional mold, a supporting frame on which the mold sections are mounted, an air motor operatively connected to the mold sections for opening and closing the mold, an air pressure line to the motor, a valve in said line controlling the air supply to said motor, an electromagnet operatively connected to said valve, means providing an electric circuit for the electromagnet, a switch in said circuit, means for actuating said switch when the mold is lowered to operative position, a second switch in said circult, a cam controlling said second switch, and means for actuating said cam in synchronism with the step movements of the carriage.

16. Thecombination of an electric motor, a shaft driven continuously thereby, a cam, driving connections between the cam and said shaft for rotating the cam at the same angular speed as said shaft, 9. second shaft geared to said first mentioned shaft for rotation at a higher speed, a carriage mounted for rotation, a Geneva wheel connected to the carriage, a driver connected to said second shaft and operable to index the Geneva wheel during a rotation of the shaft and thereby impart a step rotation to the carriage, and means to render said driver inoperative during alternate rotations of said second shaft and thereby cause the carriage to be given but one step rotation for each complete rotation of said cam.

17. The combination of an electric motor, a shaft driven continuously thereby, a cam, driving connections between the cam and said shaft for rotating the cam at the same angular speed as said shaft, a second shaft geared to said first mentioned shaft for rotation at a higher speed, a carriage mounted for rotation, a Geneva wheel connected to the carriage, a driver connected to said second shaft and operable to index the Geneva wheel during a rotation of the shaft and thereby impart a step rotation to the carriage, means to render said driver inoperative during alternate rotations of said second shaft and thereby cause the carriage to be given but one step rotation for each complete rotation of said cam, work-holders on the carriage for holding blanks of thermoplastic material, said workholders being brought in succession to heating and molding stations by the step rotations of the carriage, and a heating drum and blow mold lo-' cated respectively at said heating and molding stations.

VICTOR E. HOFMANN. JOHN M. BLANK. 

